1. Field of the Invention
The present invention relates to an engine speed control system for a working vehicle, particularly a lawn mower, having an engine, and a propelling transmission and a power takeoff device driven by the engine.
2. Description of the Related Art
In an operational run of a working vehicle, e.g. a grass cutting run of a lawn mower, the engine normally is set to a maximum rotating rate or a rotating rate close thereto. That is, the vehicle is used in an operation with an accelerator fixed to a predetermined high speed position. The rotating rate of the engine is seldom changed during an ordinary operational run. Conventionally, therefore, such a working vehicle has a pivotable throttle lever manually operable by the driver to adjust engine speed to a predetermined value.
In the case of a lawn mower, a mower unit receives drive of the engine through a power takeoff device, and the drive transmission to the mower unit is controlled by a power takeoff clutch. When the mower unit is driven again (by engaging the power takeoff clutch) after an interruption of a grass cutting operation (disengagement of the power takeoff clutch) or when the engine is started again to resume a run after the lawn mower is stopped, the engine should desirably be set to a low rotating rate, e.g. idling speed, in order to assure a smooth operation.
However, engine speed is adjusted manually as noted above, and the adjusting operation is troublesome to the driver. In actual situations, the driver seldom lowers the engine speed and the engine is started in high speed conditions. Consequently, the engine will suddenly start rotating at high speed, and so will the cutting blades of the mower unit if the power takeoff clutch is engaged then. This is undesirable from the viewpoint of durability of mechanical components. In addition, an operation is started in an unsmooth way often accompanied by intense shocks.